Electric arc burns make up a substantial portion of the injuries from electrical malfunctions. The extremely high temperatures of these arcs, about four times as high as that of the sun's surface, can cause fatal burns at up to about 5 ft (152 cm), and major burns at up to about 10 ft (305 cm) distance. Information for evaluation of the degree of hazard involved with various voltages and capacity ratings of equipment is developed and the required precautions and protective means to avoid injury from this source are outlined.

The Other Electrical Hazard: Electric Arc Blast Burns

Advances in laser, microwave, and similar technologies have led to recent developments of thermal treatments for disease and injury involving skin tissue. In spite of the widespread use of heating therapies in dermatology, they do not draw upon the detailed understanding of the biothermomechanics of behavior, for none exists to date, even though each behavioral facet is well established and understood. It is proposed that a detailed understanding of the coupled biological-mechanical response under thermal agitation will contribute to the design, characterization, and optimization of strategies for delivering better treatment. For a comprehensive understanding on the underlying mechanisms of thermomechanical behavior of skin tissue, recent progress on bioheat transfer, thermal damage, thermomechanics, and thermal pain should be systematically reviewed. This article focuses on the transfer of heat through skin tissue. Experimental study, theoretical analysis, and numerical modeling of skin thermal behavior are reviewed, with theoretical analysis carried out and closed-form solutions obtained for simple one-layer Fourier theory based model. Non-Fourier bioheat transfer models for skin tissue are discussed, and various skin cooling technologies summarized. Finally, the predictive capacity of various heat transfer models is demonstrated with selected case studies. DOI: 10.1115/1.3124646

Mathematical Modeling of Skin Bioheat Transfer

Working conditions for fire fighters can be described according to the environment temperature and the incident radiant heat flux. Measurements for this study in buildings for fire fighting training have shown that fire fighters are typically exposed to radiant heat fluxes of between 5 and 10 kWm(-2) during this kind of exercise. The heat load can nevertheless be much higher. In one case, 42 kWm(-2) was measured. The temperatures reached between 100 and 190 degrees C at 1 m above ground, going up to 278 degrees C in one case. Human trials have been performed with 17 fire fighters. After exercises (about 15 min) in a heated room, the mean core temperature of the fire fighters rose by 0.6 degrees C with a surrounding temperature of 31 degrees C and 1.0 degrees C with 38 degrees C. The sweat production varied from 0.7 to 2.1 lh(-1); 16% to 45% of sweat remained in the clothing layers. During the exercises in the training buildings, a mean of 48 degrees C has been measured between fire fighters' clothing and workwear. These conditions lead to an increase of the relative humidity in all the jackets up to 100%. When the fire fighters came out of the fire, the humidity remained at this level in the PVC coated jackets while it was in some cases strongly reduced in breathable jackets.

Fire fighting and its influence on the body.

Publisher Summary Heat transfer exhibits many therapeutic applications involving either a raising or lowering of temperature. It often requires precise monitoring of the spatial distribution of thermal histories that are produced during a protocol. The ability to perform accurate analysis of the heat transfer phenomena has led to a quantitative basis for describing the broad range of bioheat transfer processes that exist and in modeling the unique features of the flow of heat in living systems. This chapter presents a general background for the previous work in bioheat transfer. It describes the evolution of modeling techniques to deal with the special problems confronting the analysis of heat transfer processes in biosystems, both in vivo and in vitro. In specific, the chapter outlines the paths that are followed in arriving at the present state-of-the-art in several important areas of bioheat transfer modeling. It addresses the techniques for the modeling of many of the most important and commonly encountered examples of heat transfer processes in living systems.

Modeling of Bioheat Transfer Processes at High and Low Temperatures

A three-dimensional body scanning technique is used to measure the air gap layer distribution between different-sized protective garments and the body of a manikin used to evaluate garment thermal ...

Clothing Air Gap Layers and Thermal Protective Performance in Single Layer Garment

: Thermal protection rating systems for fabrics, based on pain and blister effects in human skin, are considered in terms of: (1) precise evaluations applicable to any known temperature-time pattern, and (2) simple laboratory procedures to provide a universally useful standard rating system The first system which is more comprehensive is difficult and requires computer operations routinely; the second, described in detail, offers a rating system which is simple, directly related to pain and blister parameters, and may be understood by the uninitiated as well as those knowledgeable in the field

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Method and rating system for evaluation of thermal protection.

To determine the maximum permissible temperature any material may attain without causing pain or burn on contact with bare skin, over 2000 observations were made of pain threshold during contact with materials at elevated temperatures. Six materials were used representing the full range of thermal properties from good conductors to good insulators. Time to pain threshold was converted to time to threshold blister on the basis of the relationship between pain and burn established earlier for radiant and for convective heating. Calculated times to blister were used to predict the material temperatures causative of "touch-burn". Experimentally produced threshold blisters at the predicted temperature-times verified the predictions. Graphs and equations were generated for determining safe temperatures for any material in contact with bare skin for 1-5 s solely from a knowledge of its thermal properties. Conversely, the thermal inertia (k rho c) of the optimal material for a specific use and skin contact can be predicted from a knowledge of the maximum material temperature and length of contact time anticipated.

Thermal conduction effects in human skin.

Burn production and prevention in convective and radiant heat transfer.

Flame-Contact Studies

Aerospace design engineers have long sought concrete data with respect to the thermal safety of materials in contact with human skin. A series of studies on this subject has been completed and some of the results have been reported earlier. In these studies over 2,000 observations were made of pain threshold during contact with materials at elevated temperatures. Six materials were used representing the full range of thermal properties from good conductors to good insulators. Previous reports gave methods for determining the maximum permissible temperatures for any material in safe contact with bare skin for 1-5 s solely from a knowledge of its thermal properties. This report presents the comparison of the theoretical and experimental contact temperatures at pain threshold and provides a method for deriving the skin temperature productive of threshold pain from the thermal properties of any material within the range of those studies. Ratios reflecting the heat transfer coefficient associated with the materials in contact are related to their thermal properties so that the skin temperature at pain threshold may be determined from that calculated from heat transfer theory. Tabular and graphical representation of these data permits interpolation within the range of properties so that any material of known thermal conductivity, density and specific heat may be assessed with respect to its effect on the skin temperature during contact to the end point of pain. These data, in conjunction with those already reported, constitute a system for the complete assessment of the thermal aspects of practically any material suitable for construction and manufacturing applications with respect to safe contact with human skin.

M A Chianta

Papers

Method and rating system for evaluation of thermal protection.

Thermal conduction effects in human skin.

Burn production and prevention in convective and radiant heat transfer.

Flame-Contact Studies

Prediction of threshold pain skin temperature from thermal properties of materials in contact.